Equilibrium Superelevation:

Note: This topic is part of the second chapter of Highway Engineering. I suggest reading this topic in the context of the complete chapter: Geometric Design of Highway. If you want to read the entire Highway Engineering, click here: Highway Engineering.

Equilibrium superelevation is that superelevation at which pressure at the inner and outer tyre will be equal. if the coefficient of friction is neglected i.e. f =0 then,

e=\(\frac{V^{2}}{127R}\)    , V in km/h

This means that if a road surface is super elevated by tan^-1\(\frac{V^{2}}{127R}\)  then the friction force will not be called upon to act and thus the pressure on both the wheel will be equal.

e_equilibrium =\(\frac{V^{2}}{127R}\) 

If the superelevation provided is less than e_equilibrium lateral fiction will come into play and will go on increase as the superelevation gets reduced.

Note⇒ Due to equilibrium superelevation:

• No overturning, No Toppling, No Skidding, No Sliding.
• Pressure at the inner and outer tyre will be equal.

Superelevation As Per IRC

1.Maximum Superelevation

2.The minimum superelevation

It is provided on a road must not be less than the camber of the road for the adequate drainage of water from the surface.